Toshiki Kai is a prominent character in the anime series Cardfight!! Vanguard. Known for his serious and stoic demeanor, Kai is a highly skilled and strategic cardfighter. He is often seen as a rival to the protagonist, Aichi Sendou, and plays a crucial role in Aichi's development as a cardfighter. Despite his aloof personality, Kai has a strong sense of justice and deeply cares for his friends, though he rarely expresses it openly. Throughout the series, his character evolves as he confronts personal challenges and strengthens his bonds with others.